Exploring the next step in micro-solvation of CO in water: Infrared spectra and structural calculations of (H2O)4–CO and (D2O)4–CO

• Published in: The Journal of chemical physics 2021-01, Vol.154 (4), p.044310-044310
• Main Authors: Barclay, A. J., Pietropolli Charmet, A., McKellar, A. R. W., Moazzen-Ahmadi, N.
• Format: Article
• Language: English
• Subjects: Carbon monoxide; Deuterons; High resolution; Hydrogen bonds; Infrared spectra; Infrared spectroscopy; Mathematical analysis; Physics; Solvation; Spectrum analysis
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/5.0038188

We extend studies of micro-solvation of carbon monoxide by a combination of high-resolution IR spectroscopy and ab initio calculations. Spectra of the (H2O)4–CO and (D2O)4–CO pentamers are observed in the C–O stretch fundamental region (≈2150 cm−1). The H2O containing spectrum is broadened by predissociation, but that of D2O is sharp, enabling detailed analysis that gives a precise band origin and rotational parameters. Ab initio calculations are employed to confirm the assignment to (water)4–CO and to determine the structure in which the geometry of the (water)4 fragment is a cyclic ring very similar to the isolated water tetramer. The CO fragment is located “above” the ring plane, with a partial hydrogen bond between the C atom and one of the “free” protons (deuterons) of the water tetramer. Together with the previous results on D2O–CO, (D2O)2–CO, and (D2O)3–CO, this represents a probe of the four initial steps in the solvation of carbon monoxide at a high resolution.